Carburetion

ABSTRACT

A carburetor having a constant level fuel supply and a mixing conduit has a throttle valve mounted above the fuel level. Two fuel supply circuits are provided. A first fuel circuit discharges through a nozzle located adjacent the high edge of the throttle valve and a second fuel circuit discharges fuel at a point located above the low edge of the throttle valve. The high and low edges referring to the position of the throttle when in curb idle position.

United States Patent Inventors James T. Bickhaus 1,783,217 12/1930 Broge261/53 St. Louis; 1,825,788 10/1931 Gardner.... 261/121(.2) Harold A.Carlson, Brentwood, Mo. 2,421,800 6/1947 Martin 261/62X Appl. No.731,989 2,877,003 3/1959 Goodridge et al. 261/62 Filed May 24, 19683,169,154 2/1965 Martin et al. 261/41(.4) Patented P 1971 3,201,097 8/1965 Arndt 261/41 (.4) Assignee ACF Industries, Incorporated 3,214,15010/1965 Rice 261/62 New Primary Examiner-Tim R. Miles Att0meyEdward H.Casey CARBURETION 7 Claims, 5 Drawing Figs.

US. Cl 261/41,

2 2 /6 ABSTRACT: A carburetor having a constant level fuel supply Int.Cl F02m 7/04 a d a mixing conduit has a throttle valve mounted above theField of Search 261/53, 62, fuel level, Two fuel supply circuits areprovided. A first fuel 121-2 circuit discharges through a noule locatedadjacent the high edge of the throttle valve and a second fuel circuitdischarges References C'ted fuel at a point located above the low edgeof the throttle valve. UNlTED STATES PATENTS The high and low edgesreferring to the position of the throttle 1,384,429 7/1921 Cole 261/121(.2) when i rb i e POSitiOIl.

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5% MY RD/JS E m m W mMfl Wm VBC. T W Au A 5m 5m M J CARBURETIONBACKGROUND OF THE lNVENTlON For many years carburetors used onautomotive internal combustion engines ran somewhere near stoichiometricmixture ratios or richer than stoichiometric. As used hereinstoichiometric ratio is that ratio of fuel and air delivered to acombustion space in such proportions as to result in complete combustionof both fuel and air. Where more fuel is supplied than there is air forcombustion, the mixture is said to be rich. If less fuel is suppliedthan is necessary, the mixture is said to be lean. Although combustioncan be initiated in the combustion chamber of any cylinder in aninternal combustion engine when the ratio is lean, there are limitsbeyond which combustion will be erratic or where it will not occur atall. Erratic combustion or complete failure of combustion is to beavoided because such results in an increase of noxious gases dischargedto the atmosphere by way of the exhaust system of the engine. Recentlegislation has required a reduction in the discharge of such noxiousgases and all present day fuel induction systems are being designed withthis end in view.

Much can be and has been done to improve the combustion chamber itself,the intake manifold as well as the carburetor. Even so present daycarburetors have certain deficiencies which result in undesirableoperation during at least a part of the range for which the carburetorwas designed. Present day carburetors utilize a butterfly-type throttlevalve. If more fuel is discharged on one side of this valve than on theother side there can be, and usually is, an inefficient mixing of airand fuel below the throttle valve. Moreover the throttle valve isnormally located immediately above the mounting flange of the intakemanifold so that there is minimum time and space available forcorrecting any unfavorable mixing of air and fuel.

In conventional carburetors the idle fuel system is a particularlytroublesome area. Usually in such a system fuel is supplied through anelongated port in the wall of the mixing conduit as well as by an idlefuel adjusting port located below the elongated port and also in thewall of the mixing conduit. Under many conditions of curb idle and partthrottle operation, fuel is discharged from this portion of the systemwith insufflcient velocity to project it out into the airstream with theresult that some of the fuel merely trickles down the side of the mixingconduit. Such trickling of fuel, of course, cannot result in goodvaporization and/or atomization of the fuel.

When the throttle is opened more widely the main fuel system will beginto discharge fuel and this normally is into the center of the mixingconduit at a point above the throttle valve. At part throttle operation,even though fuel is discharged in the center of the conduit, there mayyet result an unequal flow of air about the butterfly-type throttleplate so that again there is not produced below the throttle acompletely homogeneous mixture of air and fuel.

From the foregoing it is apparent that the carburetor utilizing a fuelsystem calculated to promote better mixing of fuel and air will beadvantageous.

DESCRIPTION OF THE INVENTION The carburetor herein disclosed utilizes abutterfly-type throttle valve that is removed a substantial distancefrom the mounting flange. In fact the throttle valve conveniently islocated above the fuel level in the fuel bowl. Two fuel supply circuitsare provided each of which coacts with one of the moving edges of thethrottle valve. A first of these fuel supply circuits is provided with afuel nozzle which is in part obstructed by an edge of the throttleplate. The second of the fuel supply circuits utilizes a fuel nozzlelocated immediately above the upper surface of the low side of thethrottle plate. Additionally the second fuel circuit is provided with asecond noule which by means of a metering screw provides the adjustmentrequired for setting the fuel requirements of the carburetor at normalcurb idle conditions. Additionally the carburetor is provided with afuel metering rod which is controlled by throttle position and which inturn meters all of the fuel supplied to both of the fuel circuits. Afurther fuel metering means controlled by throttle position is providedin the first fuel circuit to enable it to continue to deliver fuel overa greater range of throttle opening. Desirably the fuel nozzles of bothfuel circuits will discharge fuel inside the mixing conduit at pointsremoved from the wall of the conduit. To promote even better mixing ofthe air and fuel there is provided a venturi restriction at a pointbetween the throttle valve and the mounting flange of the carburetor.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a preferredembodiment of the carburetor.

FIG. 2 is a detail view of a fuel nozzle.

FIG. 3 is a plan view of a portion of FIG. 2.

FIG. 4 is a plan view of a two-barrel carburetor and,

FIG. 5 is a partial section showing the mounting of a twobarrelcarburetor on an intake manifold.

DETAILED DESCRIPTION A carburetor is indicated generally at 10 inFIG. 1. Carburetor l0 comprises a mixture conduit 12 which may beequipped with a venturi section 14 below the throttle and above theusual mounting flange l6. Flange I6 is used for bolting the carburetorto an intake manifold in the customary fashion. The carburetor is alsoprovided with a fuel bowl 20 equipped with customary float 21 and aneedle valve 23 for controlling the admittance of fuel to the fuel bowl.The float 21 and needle valve 23 insure that there is always maintaineda constant level of fuel in the bowl 20.

A rotatable throttle shaft 28 is located in mixture conduit 12 above thelevel of fuel in bowl 20. Mounted on shaft 28 is a throttle valve 30.Shaft 28 is also provided with a lever arm 32 which is provided with aneye 34 for connection to a throttle control rod which in turn isconnected to the usual foot pedal of an automobile.

A mechanically actuated metering rod 36 is suspended in the fuel bowl.Rod 36 is provided at its lower extremity with sections of varyingdiameter for metering fuel flow through a meteringjet 38. Rod 36 inmetering jet 38 controls the flow of fuel into passage 39. Rod 36 movesin response to movement of the throttle and as shown accomplishesmovement by way of connection to rocker arm 40 which is pivoted at 42.One end of arm 40 connects to throttle lever 32 by way of link 44. Aslever 32 rotates in a clockwise direction the link 44 is pulled down andthe rocker arm 40 pivots to raise the metering rod 36. As rod 36 movesin an upward direction a smaller diameter of the rod is placed in jet 38thereby allowing additional fuel to flow into passage 39.

At one end thereof, fuel passage 39 branches into two separate passagesand 52. Passage 50 terminates in a fuel nozzle 54 located inside themixture conduit immediately above throttle plate 30. Depending from ahorizontal portion of passage 50 is another passage 55 which terminatesin a nozzle 56 which also extends a short distance into the mixturepassage 12. An adjustment screw 57 having a tapered end 58 coacts withthe inner end of the nozzle 56 to regulate flow therethrough.

Branch fuel passage 52 extends to the opposite side of the carburetorand connects with a vertical passage 60 which in turn communicates witha horizontal passage 61 and fuel well 62. Passage 6lis provided with anair bleed 63 an economizer 64 and a second air bleed 65. A nozzle 66 ispressed into the wall of the conduit to communicate well 62 with theinterior of the mixture conduit.

Either one of air bleeds 63, can be provided with air metering means. Asshown the metering of air is done at bleed 65. A metering valve 70 isconnected to a rocker arm 71 which is pivoted at 72. An opposite end ofarm 71 is connected by way of link 74 to throttle lever 32 in such amanner that as the throttle valve is opened the metering head 70progressively closes off the bleed 65.

As shown in FIGS. 2 and 3 nozzle 66 is rectangular in shape and fitsinto a slot 31 of the throttle valve when the throttle is in the closedor curb idle position. The inner end 33 of slot 31 coacts with the outerend of noule 66 in much the same fashion as the edge of the throttleplate coacts with the idle fuel port in conventional carburetors.

The carburetor as just described is adequate for all normal runningconditions of the carburetor including the range from curb idle to wideopen throttle. No provision has been made in the carburetor as shown forcompensating for transient or temporary conditions. It will beappreciated that such things as an accelerating pump and cold startingand warmup enrichment means can be added to adjust fuel delivery fortransient and temporary changes. In this connection it may be mentionedthat control of the metering rod may be further enhanced by provisionfor further movement of the rod in response to engine manifold vacuum.Such control of a metering rod is taught in Edelen 2,329,748 dated Sept.21, 1943. Such control of the metering rod allows for maximum flow offuel whenever manifold vacuum drops below a predetermined amount such asmight occur at a part throttle condition with the engine heavily loaded.

OPERATION Assuming the engine running and at curb idle, there will he aquantity of air flowing through the carburetor sufficient to operate anengine at that condition. The throttle plate 30 is substantially closedand some air will be passing by the throttle plate. At this time airwill enter the upper portion of nozzle 66 sweep past the edge 33 of thethrottle plate picking up some fuel and discharging a mixture of fueland air below the throttle plate. On the opposite side of the mixingconduit air entering nozzle 54 picks up some fuel from passage and mixeswith the fuel in passage to be discharged through nozzle 56. Finaladjustment of idle fuel requirements is made by the adjusting screw 57.Under these conditions it is seen that the required fuel is deliverednot only from both sides of the mixing conduit but at points away fromthe conduit walls so that the air sweeping by the throttle plate picksup the fuel and thoroughly mixes with it to produce a homogeneousmixture. The venturi 14 below the nozzles further enhances the mixing ofthe air and fuel.

As the throttle valve moves away from curb idle position, nozzle 66 isopened more fully and as soon as the throttle plate is above the nozzle,nozzle 66 is then exposed to manifold vacuum and a greater flow of fuelfrom that nozzle results. Shortly after the throttle plate clears thenozzle 66, fuel begins to flow from nozzle 54. This is so because airsweeping by nozzle 54 creates a negative pressure at the end of thenozzle and this negative pressure is enough to start fuel flow. At thistime fuel will be flowing from noule 66, nozzle 54 and nozzle 56 but asbefore all fuel is discharged at points removed from the wall of theconduit whereby most efficient mixing of fuel and air results.

As the throttle opens more widely and with fuel being delivered from allthree of the nozzles as described, the mechanical connection of themetering rod to the throttle lever withdraws metering rod 36 from thejet 38 to position a diameter of the end of rod 36 in the jet such thatthe correct quantity of fuel will flow into passage 39. Of course, atwide open throttle the smallest diameter of the rod 36 is in the jet.The fuel in passage 39 is still distributed to all three of the nozzles54, 56 and 66.

Once throttle 30 has cleared the nozzle 66, fuel flow normally would beexpected to decrease from that nozzle. However, this is not so becausevalve 70 in response to throttle movement begins to close off the idlebleed 65. Shutting off the flow of air at bleed has the effect ofenrichening the mixture in the cavity 62 which results in more fuelflowing from the nonle 66. In other words, valve member and the bleed 65constitute a metering arrangement for the fuel system which deliversfuel to nozzle 66. It would be possible to achieve this metering inother manners as for example use ofa variable orifice at the economizer64, use of a valve similar to 70 at air bleed 63. Or even a metering rodinstalled in the passage 60.

The carburetor just described has many advantages over prior artconventional carburetors. Placement of the fuel nozzles away from theconduit wall insures that there will be intimate mixing of air and fuelas the air sweeps by the throttle plate. Moreover in the part throttleranges the quantities of air and fuel flowing on each side of thethrottle plate are more nearly equal than has been possible heretofore.This is especially important when considering exhaust emissions becausemost driving in the large metropolitan areas where smog is a problem isrestricted to speeds below 50 mph Of course a speed of 50 mph. is only apart throttle range for the carburetor. lt is also to be mentioned thatthe mixing and hence ultimate distribution to the individual cylindersis further enhanced by the venturi section 14 which is located wellbelow the throttle plate and below the noules.

The carburetor as just described can also be fabricated into a twooreven a four-barrel carburetor. A two-barrel version is shown in planview in FIG. 4 where identical barrels of a two-barrel carburetor aremounted side-by-side. The numerals applied to the carburetor are thesame as the numerals applied in FIG. 1 excepting that the numerals forone side of the carburetor bear the superscript A.

FIG. 5 shows a portion of an intake manifold such as is commonly usedwith V-8 engines. Mixing conduit 12 of the two-barrel carburetordischarges the mixture of air and fuel into a plenum 82 from whence abranch passage 83 conducts the mixture to the respective cylinders. insimilar manner mixing conduit 12A discharges into a plenum 84 whichconducts the mixture to the various cylinders by way of branch passage85. It is common practice with V-8 engines to separate the respectivemixing chambers so that one bank of cylinders will be served by one ofthe mixing conduits and the other bank of cylinders will be served bythe other mixing conduit. In some instances the intake manifolds arearranged so that the plenum of one portion of the intake manifold willserve two cylinders on one side of the engine and two additionalcylinders on the other side of the engine. However, this is a matter ofchoice with the individual engine designer and either system can beused.

lt will be appreciated that various modifications can be made to thecarburetor described above without departing from the full intent andscope of the invention which is defined in the appended claims.

We claim:

1. A downdraft carburetor comprising a bore including a mixing chamber,a constant level fuel supply, and a butterflytype throttle valve theimprovement characterized in that;

a. The throttle valve is positioned near the level of fuel in the saidconstant level fuel supply thereby leaving an elongated mixing zonebelow the throttle valve,

b. the said throttle valve having a high side and a low side.

0. a first fuel circuit for supplying fuel adjacent the high side of thethrottle valve,

d. a second fuel circuit for supplying fuel in the vicinity of the lowside of said throttle valve, and

3. at least one air bleed for the said first fuel circuit and furtherincluding fuel enrichment means in said air bleed, said fuel enrichmentmeans comprising a tapered metering element and being connected bybellcrank and connecting rod means to said throttle for movementtherewith.

2. The carburetor of claim 1 including a restricted zone comprising aventuri located below the said throttle.

3. The carburetor of claim 1 including a nozzle for the said first fuelcircuit, the said nozzle projecting a short distance into the saidmixing chamber for a progressive coaction with the said high side of thesaid throttle whereby fuel delivery increases as said throttle opens.

6. The carburetor of claim 5 including idle fuel adjustment meanscooperable with said lower tube.

7. The carburetor of claim 1 in which the said first and second fuelcircuits are branch passages from a main fuel supply well and the saidwell is provided with an entrance having a throttle position controlledmetering rod.

1. A downdraft carburetor comprising a bore including a mixing chamber,a constant level fuel supply, and a butterfly-type throttle valve theimprovement characterized in that; a. The throttle valve is positionednear the level of fuel in the said constant level fuel supply therebyleaving an elongated mixing zone below the throttle valve, b. the saidthrottle valve having a high side and a low side. c. a first fuelcircuit for supplying fuel adjacent the high side of the throttle valve,d. a second fuel circuit for supplying fuel in the vicinity of the lowside of said throttle valve, and
 3. at least one air bleed for the saidfirst fuel circuit and further including fuel enrichment means in saidair bleed, said fuel enrichment means comprising a tapered meteringelement and being connected by bellcrank and connecting rod means tosaid throttle for movement therewith.
 2. The carburetor of claim 1including a restricted zone comprising a venturi located below the saidthrottle.
 3. at least one air bleed for the said first fuel circuit andfurther including fuel enrichment means in said air bleed, said fuelenrichment means comprising a tapered metering element and beingconnected by bellcrank and connecting rod means to said throttle formovement therewith.
 3. The carburetor of claim 1 including a nozzle forthe said first fuel circuit, the said nozzle projecting a short distanceinto the said mixing chamber for a progressive coaction with the saidhigh side of the said throttle whereby fuel delivery increases as saidthrottle opens.
 4. The carburetor of claim 3 including a slot in thesaid high side of said throttle, said slot partially surrounding saidnozzle.
 5. The carburetor of claim 1 including upper and lower fueldischarge tubes for said second fuel circuit, the said upper tubepositioned above the low side of said throttle and the said lower tubepositioned below the said throttle and both of said tubes dischargingfuel away from the wall of said bore.
 6. The carburetor of claim 5including idle fuel adjustment means cooperable with said lower tube. 7.The carburetor of claim 1 in which the said first and second fuelcircuits are branch passages from a main fuel supply well and the saidwell is provided with an entrance having a throttle position controlledmetering rod.